The State We're In
Acorn booms and busts – a nutty tale
By Alison Mitchell, Co-Executive Director
If you’re out this fall enjoying your yard, strolling through neighborhood streets or city parks, or hiking along wooded trails, you may have spotted lots of acorns, hickory nuts or beech nuts on the ground. Or maybe you noticed the opposite – a lack of acorns and other nuts in places they were once plentiful.
It’s not your imagination! Trees produce nuts in irregular cycles, with boom and bust years. Sometimes they’re so abundant that it looks like someone dumped a truckload. Other years, it seems like the trees decided to take a vacation.
There’s a name for what’s happening with the trees: masting. “Mast” is the term for the fruit of forest trees and shrubs. During “mast” years, trees go into overdrive, producing enormous amounts of nuts. Mast years are usually followed by a year or more of scant production.
Why does this happen? It’s a natural cycle, though it’s somewhat of a mystery why trees mast when they do, and how trees of the same (and sometimes different) species are often able to synchronize their timing within a region.
In New Jersey and beyond, acorns – the nuts of oak trees – are by far the largest crop. Oaks in North America produce more nuts than all other native trees put together. There are about 90 species of oak in North America, including 19 in New Jersey, and all produce acorns. During a mast year, large oaks can make up to 10,000 acorns, ten to twenty times more than average.
Contrary to one nature myth, a fall bumper crop of acorns isn’t necessarily a harbinger of a cold, harsh winter.
Scientists don’t know the exact trigger for mast years, but it most likely has to do with climate events in past stressful years. Trees may produce an abundance of offspring as a hedge in case the stressful times continue. Stressors may include droughts, heat waves, or cold spells.
Mast years don’t happen only in New Jersey or North America; they take place all over the world, in dozens of species of unrelated trees, even in the tropics. Underground communication along fungal networks connecting the roots of many different species may aid the synchronization of the mast phenomenon.
In his new book, “The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees,” ecologist and college professor Dr. Douglas Tallamy discusses how trees benefit from mast years.
It has to do with “predator satiation,” or making sure there are enough acorns to overwhelm hungry seed predators. If nut production is regular and predictable, animals will consume all the nuts and there won’t be any left to grow new trees. But in a particular year, if trees simultaneously produce far more nuts than can be eaten and destroyed, there will be plenty left to successfully sprout.
In years with overabundant nuts, the animals that feed on them do well, including deer, bears, squirrels, chipmunks, birds and insects. Animal populations increase. During cycles when nuts aren’t plentiful, animals eat virtually all the nuts but their populations decline due to malnutrition and poor reproductive rates.
Then, when a mast year finally occurs again, there aren’t enough seed predators left to fully consume the plethora of nuts. It’s a never-ending accidental war between trees that produce a nutritious item to attract dispersal agents like squirrels, without constantly keeping the squirrels so well-fed that they kill nearly all of the tree’s offspring!
When animals consume nut crops, they accidentally assist in a tree’s reproduction by spreading nuts away from the parent tree. Many mammals and birds – including jays and red-headed woodpeckers – carry nuts away and stash them in hiding places for future use. Some die over the winter, leaving their stashes untouched. Because the nuts are unevenly hidden, they’re less likely to be discovered by other seed predators.
New Jersey has a number of deciduous trees that produce nuts. In addition to attracting wildlife, many nuts are tasty to humans:
Oaks – Oak trees fall into two broad groups, white oaks and red oaks. Acorns produced by the white oak group are longer and narrower, and start sprouting in the fall; acorns from the red oak group are rounder and don’t sprout until the next spring. Squirrels know which is which, and will nip off germinating rootlets of white oak acorns so they can’t sprout. Acorns from white oaks are sweet enough to appeal to people, while red oak acorns are bitter from the tannins they contain but still sought by wildlife.
Hickories – Shagbark hickory trees produce delicious nuts prized by human foragers, but they’re notoriously hard to crack to extract the nut meats. Squirrels, chipmunks and other critters have no such problem. Among the hickories native to New Jersey are the swamp hickory and bitternut hickory, whose nuts are too bitter for human enjoyment.
Chestnuts – American chestnuts once dominated forests and produced massive crops of delicious nuts, but are functionally extinct due to a blight that virtually wiped out their populations a century ago. Although Chinese and Spanish chestnuts are now common landscape plants, efforts to breed blight-resistant American chestnuts continue.
Others – Nut-bearing New Jersey trees also include native beech, black walnuts, and now-rare butternuts, all of which appeal to human tastes. American hazelnuts and beaked hazelnuts are also native to this state we’re in, but they are shrubs, not trees. Their nuts, also known as filberts, are a delicious find for human and wildlife foragers alike.
Time will tell whether 2022 will be a mast year for New Jersey trees. Since mast years can vary geographically and from species to species, there may be bumper crops of some nuts in some places.
What’s happening near you? Keep your eyes peeled! Observing nature is one of the joys of spending time outdoors – and you may even find some yummy nuts to take home!
For more information about New Jersey trees, go to the American Chestnut Foundation website at https://acf.org/ or the NJ Forest Resource Education Center (FREC) in Jackson at www.nj.gov/dep/parksandforests/forest/education/frec.html.
About the Authors
John S. Watson, Jr.
Michele S. Byers
Executive Director, 1999-2021
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